Method of dispersing an insoluble material in aqueous solution and agricultural formulation

ABSTRACT

A method of dispersing an insoluble material in an aqueous solution comprising the following steps:
     (i) providing a formulation comprising at least one insoluble material and at least one dispersant comprising a water soluble agriculturally acceptable derivative of an alternating copolymer or an agriculturally acceptable salt thereof wherein said alternating copolymer comprises at least one residue of a first comonomer and at least one residue of a second comonomer, wherein said first comonomer comprises αβ-unsaturated oxyacids or anhydrides and said second comonomer comprises olefinic compounds containing one or more polymerizable double bonds; and   (ii) dispersing said formulation in an aqueous medium.

The present invention relates generally to dispersants, for use in agricultural applications, in particular the present invention relates to methods for the dispersion of insoluble material with copolymeric dispersants which dispersions are formed with improved dispersibility and show improved suspensibility. The present invention also relates to methods of producing dispersible formulations, the formulations per se and methods of treating substrates with dispersions produced from such formulations.

The active principles in many agricultural applications are largely hydrophobic or water insoluble in character and are, by necessity, often administered as finely divided solids suspended in aqueous media. The majority of these active principles are manufactured and marketed in concentrated form, possibly with the addition of other insoluble inert fillers, which are then diluted prior to application. For example, the active principle is typically available in the form of a suspension concentrate (SC), wettable powder (WP) or water dispersible granule (WG). However, due to the generally hydrophobic nature of the active principle, the addition of a suitable dispersant is essential in order to achieve an homogenous dispersion with a minimum of mixing, such as may be achieved readily by hand or with minimal mechanical mixing. Furthermore, once an homogenous dispersion is achieved, the resulting suspension must remain stable for a time sufficient, at least, to allow application by usual means such as spraying. Any settling, agglomeration or flocculation of the finely divided solid may lead to inconsistent and ineffective application as well as blockage of the spraying equipment. It is therefore necessary to provide a dispersant which provides easy and homogenous dispersion and results in a suspension which maintains its stability during the application of the aqueous dispersion.

Effective dispersants for use in these applications ideally provide a suspension with acceptable dispersibility, suspensibility and lack of agglomeration. The Collaborative International Pesticides Analytical Council (CIPAC Handbook Volume 1) defines methods that can be used for determining acceptable suspensibility (MT 15.1) and degree of agglomeration (MT 59.3). For example, in suspension concentrates so-called SC formulations, this can be achieved by the addition of about 3-5 w/w % of a standard dispersant. Wettable powder (WP) and water dispersible granule (WG) formulations generally require the addition of standard dispersant in the order of 6-7 w/w % in order to achieve acceptable suspensibility and degree of agglomeration as determined by a wet sieve retention test. (MT 59.3).

Currently used dispersants for SC formulations include ethylene oxide/propylene oxide block copolymer surfactants based on an hydrophobic moiety plus ethyleneoxide. Also used are ether phosphate derivatives of non-ionic surfactants, especially of tristyrylphenol ethoxylates. Conventional anionic surfactants used include sulphonated derivatives of arylformaldehyde condensates, polyacrylates and lignosulfonates.

Dispersants for WP and WG formulations are usually limited by the requirement that the dispersant be solid at ambient temperatures, be non-gelling and not dissolve the active principle. For these reasons, conventional non-ionic surfactants are often unsuitable, and anionic dispersants are preferred. Known effective dispersants for WP and WG formulations include sulphonated alkylnaphthalene/formaldehyde condensate salts and lignosulfonate salts.

α-Olefin-polycarboxylate copolymers are well known as dispersants in a wide range of applications including pigment dispersion, emulsion polymerisation, cosmetics and pesticidal compositions. As far back as 1972 the sodium salt of a maleic anhydride and diisobutylene copolymer was given an exemption from tolerance for use in pesticide formulations by the United States. Environmental Protection Authority following a petition from Rohm and Haas Co. FR 2545325 describes the use of ammonium and alkali metal salts of maleic anhydride-diisobutylene copolymer in pesticide granules. Similarly, EP 201417 describes the use of copolymers of maleic anhydride with surfacants selected from sulfates and phosphates of ethoxylated phenol derivatives in WP and WG formulations. JP 62036302 describes copolymers having a molecular weight range of from 5000-20000 for use with granular agrochemical compositions. Maleic anhydride and diisobutylene copolymer derivatives are described for use in conjunction with CaCO₃ and Mg salts for SC formulations in JP 06 09,302. The use of sulfonated derivatives of copolymers of maleic anhydride in water dispersable granules is also described in JP 58-131903.

French Patent No. 2,397,444 describes stable and concentrated dispersions of active materials which may be prepared from non-dusting powders or granular materials. It is necessary to separate the active material in the presence of a salt of an acidic resin, such as, for example, a copolymer of maleic anhydride and an α-olefinic compound; add an organic solvent which forms, together with the aqueous medium, a two-phase system; treat such two-phase system by adding a carrier substance thereto; and then isolate the product by a reduction in the volume of the organic phase by the addition of water, the solvent gradually transferring into the added water.

We have now found that the use of a range of derivatisations of alternating copolymers of an α,β-unsaturated oxyacid and an olefin having one or more polymerizable double bonds provides improved dispersibilty and suspensibility in agrochemical formulations, compared to those dispersants already described in the prior art, as well as a number of other ancillary benefits which will be more fully described herein.

According to a first aspect of the present invention, there is provided a method of dispersing an active water-insoluble agrochemical principal in an aqueous solution comprising the following steps:

-   (i) providing a formulation comprising at least one active     water-insoluble agrochemical principal and at least one dispersant     comprising a water soluble agriculturally acceptable derivative of     an alternating copolymer or an agriculturally acceptable salt     thereof wherein said alternating copolymer comprises at least one     residue of a first comonomer and at least one residue of a second     comonomer, wherein said first comonomer comprises α,β-unsaturated     oxyacids or anhydrides and said second comonomer comprises olefinic     compounds containing one or more polymerizable double bonds, with     the proviso that the alternating copolymer is not a copolymer of     maleic anhydride and diisobutylene; and -   (ii) dispersing said formulation in an aqueous medium.

According to a second aspect of the present invention, there is provided a method of making an agrochemical formulation comprising the steps of:

-   (i) combining at least one insoluble material, and at least one     dispersant comprising a water soluble agriculturally acceptable     derivative of an alternating copolymer or an agriculturally     acceptable salt thereof wherein said alternating copolymer comprises     at least one residue of a first comonomer and at least one residue     of a second comonomer, wherein said first comonomer comprises     α,β-unsaturated oxyacids or anhydrides and said second comonomer     comprises olefinic compounds containing one or more polymerizable     double bonds, with the proviso that the alternating copolymer is not     a copolymer of maleic anhydride and diisobutylene; -   (ii) milling said combination to a particle size range in order to     obtain a stable, readily-suspendible aqueous dispersion; and -   (iii) stabilising said aqueous dispersion to obtain an SC     formulation suitable for dilution in water for agricultural use.

According to a third aspect of the present invention, there is provided a method of making an agrochemical formulation comprising the steps of:

-   (i) combining at least one insoluble material, with at least one     dispersant comprising a water soluble agriculturally acceptable     derivative of an alternating copolymer or an agriculturally     acceptable salt thereof wherein said alternating copolymer comprises     at least one residue of a first comonomer and at least one residue     of a second comonomer, wherein said, first comonomer comprises     α,β-unsaturated oxyacids or anhydrides and said second comonomer     comprises olefinic compounds containing one or more polymerizable     double bonds, with the proviso that the alternating copolymer is not     a copolymer of maleic anhydride and diisobutylene; and -   (ii) milling said combination to a desired particle size to obtain a     homogeneous wettable powder (WP) formulation.

According to a fourth aspect of the present invention, there, is provided a method of making an agrochemical formulation comprising the steps of:

-   (i) combining at least one insoluble material suitable for     agricultural use with at least one dispersant comprising a water     soluble agriculturally acceptable derivative of an alternating     copolymer or an agriculturally acceptable salt thereof wherein said     alternating copolymer comprises at least one residue of a first     comonomer and at least one residue of a second comonomer, wherein     said first comonomer comprises α,β-unsaturated oxyacids or     anhydrides and said second comonomer comprises olefinic compounds     containing one or more polymerizable double bonds, with the proviso     that the alternating copolymer is not a copolymer of maleic     anhydride and diisobutylene; and -   (ii) blending said combination to obtain a homogeneous wettable     powder (WP) formulation.

According to a fifth aspect of the present invention, there is provided a method of making an agrochemical formulation comprising the steps of:

-   (i) combining at least one insoluble material suitable for     agricultural use with at least one dispersant comprising a water     soluble agriculturally acceptable derivative of an alternating     copolymer or an agriculturally acceptable salt thereof wherein said     alternating copolymer comprises at least one residue of a first     comonomer and at least one residue of a second comonomer, wherein     said first comonomer comprises α,β-unsaturated oxyacids or     anhydrides and said second comonomer comprises olefinic compounds     containing one or more polymerizable double bonds, with the proviso     that the alternating copolymer is not a copolymer of maleic     anhydride and disobutylene; -   (ii) agglomerating said combination to form discrete granular     materials; and -   (iii) drying said granular materials to obtain a water dispersible     granule WG formulation.

According to a sixth aspect of the present invention, there is provided a formulation produced by the process of the second, third, fourth and fifth aspects.

According to a seventh aspect of the present invention, there is provided an agricultural formulation comprising at least one insoluble material and at least one dispersant comprising a water soluble agriculturally acceptable derivative of an alternating copolymer or an agriculturally acceptable salt thereof wherein said alternating copolymer comprises at least one residue of a first comonomer and at least one residue of a second comonomer, wherein said first comonomer comprises αβ-unsaturated oxyacids or anhydrides and said second comonomer comprises olefinic compounds containing one or more polymerizable double bonds, with the proviso that the alternating copolymer is not a copolymer of maleic anhydride and diisobutylene.

According to an eighth aspect of the present invention, there is provided a method of treatment of a substrate with an active water-insoluble agrochemical principal comprising the following steps:

-   (i) preparing a formulation comprising at least one active     water-insoluble agrochemical principal and at least one dispersant     comprising a water soluble agriculturally acceptable derivative of     an alternating copolymer or an agriculturally acceptable salt     thereof wherein said alternating copolymer comprises at least one     residue of a first comonomer and at least one residue of a second     comonomer, wherein said first comonomer comprises α,β-unsaturated     oxyacids or anihydrides and said second comonomer comprises olefinic     compounds containing one or more polymerizable double bonds, with     the proviso that the alternating copolymer is not a copolymer of     maleic anhydride and diisobutylene; -   (ii) dispersing said formulation in an aqueous medium; and -   (iii) applying the dispersed formulation to a substrate.

The dispersants for use in the present invention are based on alternating copolymers. It will be understood by those skilled in the art that alternating copolymers may be prepared by the careful selection of comonomers and reaction conditions. As is well known in the art, often additional polymerization conditions should be observed in order to obtain an alternating copolymer. For example the temperature and type of solvent can influence whether an alternating or other type of copolymer is formed. Methods for making such alternating copolymers will be well known to those skilled in the art of polymer synthesis.

The alternating, or substantially alternating character, of the copolymers is believed to be critical to the present invention. The person skilled in the art will understand the degree of regularity necessary in order for a copolymer to be considered of alternating character. It is preferred that the alternating copolymer has an alternating character defined by greater than 70% of consecutive comonomer residue units being alternate between residues of the first comonomer and the second comonomer, more preferably greater than 90%. A high degree of control in the synthesis of such copolymers is required in most cases to achieve this.

The alternating copolymer may contain additional comonomer residues. For example, the addition of a small amount, say less than 10%, of methyl methacrylate will not substantially change the alternating character of the copolymer. Suitable alternating copolymers for use in the present invention also include copolymers of three or more comonomers including the first and second comonomer types. While not wishing to be bound by theory it appears that providing a consistent hydrophobic polymer backbone is provided in the presence of regularly spaced anionic charge or steric barrier along the polymer molecule such as obtained by an alternating copolymer, the improved dispersant performance is preserved.

Copolymers with substantially regularly spaced anionic charges along the polymer molecule provide advantageous dispersant performance. For example the alternating, or repeating, units are preferably monomers but may also be dimers, trimers or small oligomers.

While not wishing to be bound by theory, it is believed that the stiffness of the polymer molecule is related to its performance as a dispersant. It is believed that improved dispersant performance is related to the degree of steric hindrance and the resistance of copolymer to free rotation.

Alternating copolymers may be made by copolymerising a first comonomer, or mixture of first comonomers, having at least one reactive double bond wherein the balance of substituents on the double bond make the double bond electron deficient compared to styrene, which is used by those proficient in the art of polymer chemistry as a benchmark monomer, (ref. Polymer Handbook, section 11/267), together with a second comonomer having at least one double bond that is copolymerisable with the first comonomer wherein the balance of substituents on the double bond of the second comonomer are such as to make the double bond electron rich compared to the double bond of the first comonomer.

Examples of suitable preferred first comonomers include fumaric acid, maleic acid and anhydrides, and the esters, amides and imides derived from them, itaconic acid and anhydride and the corresponding esters amides and imides derived from them, acrylic and methacrylic acids, esters and amides, vinylphosphonic acid and the corresponding esters and amides derived from it and ethylene sulphonic acid and the esters and amides derived from it.

Examples of preferred second comonomers include styrene and its alkyl and halo derivatives, vinyl ethers and esters, α-olefins, internal olefins, cyclic olefins, both exocyclic and endocyclic, allylic alcohols and their corresponding ester derivatives, allylic ethers and allylic halo compounds, allylic aryl compounds, vinyl amides, vinyl chloride and vinylidene chloride.

While not wishing to be bound by theory it is believed that the imbalance of electron deficient and electron rich double bonds of first and second comonomers confers a substantially alternating character to the copolymers derived therefrom as opposed to random or block homopolymerisation character. While not wishing to be bound by theory it appears that the alternating character of the copolymer derivatives provides either a consistent and regular charge density or a steric barrier to aid dispersant performance and also afford improved water solubility.

The dispersants of the present invention are agriculturally acceptable salts or water-soluble agriculturally acceptable derivatives of the alternating copolymer and are preferably readily soluble in water. Suitable agriculturally acceptable salt derivatives include those obtained by reacting groups pendant to the copolymer such as acids and acid derivatives, such as anhydrides and esters, with basic reagents such as alkali and alkaline earth metal hydroxides, oxides, carbonates and alkoxides, or basic nitrogen, sulphur and phosphorous compounds such as ammonia, amines and tetraalkylammonium, sulphonium and phosphonium salts. While agriculturally acceptable salts of the alternating copolymer are generally preferred, the free acid of the alternating copolymer may be provided in the formulation and a separate source of suitable cations which on addition to aqueous media solubilises the alternating copolymer.

Preferably the amount of suitable cations is sufficient to provide optimum dispersant characteristics in the alternating copolymer. It is generally desirable to provide an excess of cations such that a substantial amount of the alternating copolymer forms polyanionic polymer. The anhydride of the alternating copolymer is not generally soluble in water.

However, we have found that the free acid shows a degree of solubility in water. In one embodiment the formulation may contain the free acid of the alternating copolymer (in the absence of any suitable cation source). A cation source may be provided in a separate addition to the aqueous medium prior to the dispersing of the formulation.

We have found that certain combinations of free acids of the alternating copolymer with separate addition of a cation source prior to dispersing the formulation are advantageous. it is believed that the reaction between the free acid and the cation source generates gas and the action of which facilitates the disintegration of the granules containing the insoluble material. In particular, the addition of sodium carbonate leads to the generation of carbon dioxide and results in improved disintegration of the granules. Other cation sources may be selected so as to generate a variety of gaseous reaction products to provide improved dispersion.

Cation sources suitable for incorporation into either the formulation or the aqueous medium include sources of agriculturally acceptable cations, such as alkali metal cations. Preferably the cation source is selected from the group consisting of alkaline salts such as carbonates, bicarbonates, hydroxides, phosphates, alkoxides, borates, sulphites and silicates. Other water soluble agriculturally acceptable derivatives of the alternating copolymer include polyalkyleneoxy derivatives, polyamide derivatives and polyvinyl alcohol derivatives. By water-soluble it is meant that the derivatives of the alternating copolymer are at least partially water-soluble at ambient temperatures. Other water-soluble derivatives of the alternating copolymer are also useful in the present invention.

The preferred molecular weights of the alternating copolymers are in the range of from 1000 to 90000 daltons. We have found that certain higher molecular weight alternating copolymers show a certain degree of intractability in solution and our more preferred range is from 1000-30000 daltons, even more preferred is 1000-10000 daltons.

We have found that agriculturally acceptable salts or other water soluble derivatives of alternating copolymers for use as dispersants in agricultural compositions provide improved and consistent dispersant performance when compared to conventionally used dispersants such as sulphonated alkylnaphthalene formaldehyde condensate salts.

It is surprising that copolymers as described herein give enhanced performance when compared to previously described dispersants structures in the prior art such as for example diisobutylene, isobutylene and styrene copolymers with maleic anhydride while still other derivatives described in those same publications, cannot be reasonably used as dispersants in agricultural applications at all. For example we have found that some styrene-maleic anhydride copolymer derivatives resulted in a less stable and sometimes unstable dispersion.

It would appear that alternating character alone will not guarantee effective performance of the dispersant copolymer, for example a copolymer of methylvinyl ether and maleic anhydride gives an unstable dispersion. While not wishing to be bound by theory it appears this is due to presence of a small hydrophobic backbone, a low molecular weight or a combination thereof.

Similarly some linear α-olefin maleic anhydride derivatives such as those derived from n-ctene and n-decene also yielded unstable dispersions affording poor suspensibility. While not wishing to be bound by theory, it appears the linear conformation of the hydrophobic side chain in such polymers may either lead to ineffective binding to hydrophobic surfaces or alternatively to cross linking of binding between different surfaces. In either case flocculation is observed.

The performance of the copolymers described herein has been observed at different dispersant concentrations in WP and WG formulations to exhibit improved storage stability. Also we have found that in many cases it is possible to lower the dispersant concentration from normally accepted levels and retain an acceptable suspensibility result, thereby achieving more efficient the surface coverage of the dispersant. In practical terms this means the dispersant will be more cost effective to the end user. When the use rate of copolymers is compared to that of a diisobutylene maleic anhydride sodium salt of similar molecular weight typically we have found that the copolymers of this invention may give acceptable stability at a concentration lower than the corresponding diisobutylene derivative. In addition the formulations typically show improved dispersibility. When compared to sulfonated alkyl naphthalene formaldehyde condensates, suspensibility is significantly improved, even at lower concentrations.

Methods for making such alternating copolymers will be well known to those skilled in the art of polymer synthesis.

The dispersant system used in the present invention may be a mixture of the alternating copolymer with other dispersants known to those skilled in the art, including alkyl substituted and unsubstituted sulfonated naphthalene formaldehyde condensate salts, alkyl substituted and unsubstituted phenol formaldehyde condensate salts, lignosulphonate salts, polyacrylate salts, and other previously disclosed α-olefinic-unsaturated dicarboxylic acid copolymer derivatives.

In agrochemical applications, a wide variety of insoluble materials such as active principals are delivered in aqueous suspension. Active principals such as those used in WP, WG and SC formulations are generally insoluble at ambient temperatures. Water insoluble materials which may advantageously be used in WP, WG and SC formulations include herbicides, insecticides, fungicides, biocides, molluscicides, algaicides, plant growth regulators, anthelmintics, rodenticides, nematocides, acaricides, amoebicides, protozoacides, crop safeners and adjuvants. Examples of such actives commonly granulated or made as powders in agriculture include: triazine herbicides such as simazine, atrazine, terbuthylazine, terbutryn, prometryn and ametryn, urea herbicides such as diuron and fluometron, sulphonyl urea herbicides such as chlorsulfuron, metsulfuron methyl, nicosulfuron and triasulfuron, sulphonanilide herbicides such as flumetsulam, organophosphate insecticides such as azinphos methyl, chlorpyrifos, sulprofos and azamethiphos, carbarnate insecticides such as aldicarb, bendiocarb, carbaryl and BPMC, synthetic pyrethroids such as bifenthrin, as well as various types of fungicides including dimethomorph, benomyl, carbendazim, mancozeb, triazoles such as hexaconazole and diniconazole, acaricides such as propargite. A list of such products can be drawn from the Pesticide Dictionary (contained in the Farm Chemicals Handbook) or the British Crop Protection Society: Pesticides Manual.

In addition, some fertilizers and also water soluble active principles may use water dispersible formulations either by addition of inert carriers for convenience in handling or to aid in a controlled release formulation.

A wide variety of other insoluble materials are used in agricultural applications including fillers and carriers, for example but not limited to, natural and synthetic silicates and silicate minerals, mineral oxides and hydroxides and also natural and synthetically derived organic materials. Such materials may be added as porous carriers, as moisture inhibition agents, to aid binding or agglomeration properties of a formulation or simply to fill a formulation to a convenient weight. Examples of such fillers may include natural silicates such as diatomacious earth, synthetic precipitated silicas, clays such as kaolin, attapulgites and bentonites, zeolites, titanium dioxide, iron oxides and hydroxides, aluminium oxides and hydroxides, or organic materials such as bagassc, charcoal, or synthetic organic polymers. These other insoluble materials may be readily dispersed in accordance with the present invention.

An additional agent conventionally used in combination with dispersants used in the above formulations is a surfactant wetting agent. The role of the wetting agent in the case of SC formulations is to aid removal of air from particle surfaces during manufacture and to aid dilution in water. In the case of WP formulations the role of the wetter may be to aid penetration of the solids into water, while in the case of WG formulations it may aid penetration of the granules into water and aid disintegration of granules back to primary particle size. In some cases the dispersant may itself function as a suitable wetting agent while in others the dispersant may show an antagonistic effect on the wetter. As a further embodiment of the present invention at least one surfactant wetting agent may be selected from the group consisting of an alkylpolysaccharide; di or mono alkyl sulphosuccinate derivative; a nonionic surfactant loaded onto an inert silicate carrier; and a non-ionic surfactant delivered in the form of a urea surfactant complex.

The step of dispersing the formulation in an aqueous medium may be achieved by any convenient means dependent on the nature of the formulation. It is desirable that the dispersion of the formulation in an aqueous solution may be conducted either by hand or with a minimum of mechanical agitation. Mechanical agitation may include stirring, mixing, blending and other similar processes.

The suspension of insoluble material in aqueous medium will be typically used for the treatment of a substrate such as plant or other agricultural medium. The application of the suspension onto the substrate may be achieved by any convenient means, including spraying, and the like. Granules are generally dispersed in water prior to being sprayed by the farmer. Farm sprays may be as a small back-pack handspray or a large boom spray or other convenient means. Aerial spraying is also sometimes used.

Formulations of the present invention may also be applied to the substrate directly, prior to dispersion. The subsequent application of rain or other aqueous media is sufficient for the formulation of the suspension of particulate material.

The present invention is described with reference to WP, WG and SC formulations. In each case, formulations provide a stable aqueous dispersion of finely milled insoluble hydrophobic particles. The stability properties of the dispersion and hence the effectiveness of the dispersion can be measured by means of a suspensibility test as described by the CIPAC test MT 15.1. In this test the volume fraction of suspended material is compared to that which has settled out due to gravity after 30 minutes. Typically a dispersant with a reported percentage suspensiblity of about 80% would be considered as an effective dispersant for WG and WP formulations, while in excess of 90% would be expected for an SC formulation. Another measure of the stability of the dispersion is the degree to which particles remain non aggregated. This may also be a property of the even distribution of the dispersant in the formulation. The degree to which particles may be aggregated is often measured by a wet sieve retention test as described in CIPAC test MT 59.3. In this test the dispersed solid is poured through a series of fine sieves and retained material is measured as a fraction of the total amount of dispersed material. Formation of such aggregates is a major problem observed in WG formulations and to a lesser extent in WP formulations.

Generally WP formulations are produced by milling the active principle either alone or in combination with fillers, dispersants and/or surfactant wetters to a suitable particle size, typically in the 5-15 μm range. The milled material is then dry blended with a surfactant wetter, and/or dispersant if not already present or with additional dispersants and/or surfactant wetters to give a homogeneous composition. The powder formulation is assessed for wettability according to a method such as CIPAC MT 53.5.1 and suspensibility as per CIPAC MT 15.1. A formulation will desirably have a wettability of less than 1 minute and a suspensibility above 80%. Below 60% would generally be considered unacceptable. Results which might be commercially acceptable are either determined by the local registration authority or by the standards set by the formulators themselves.

In the case of WG formulations a suitably milled active ingredient with or without other fillers, typically of particle size 5 to 15 μm. may be mixed with one or more surfactant wetters and one or more dispersants. Typically an excess of water is added to bind the particles together into agglomerates. The excess water is later reduced by suitable air drying techniques to an optimal level.

The agglomerates are typically granulated using one of many techniques including pan granulation, drum granulation, fluid bed granulation, spray drying, tableting or extrusion techniques which are well known to those skilled in the art.

The wetter and dispersant may either be powder blended with the active ingredient or alternatively blended as an aqueous solution in the water used to aid agglomeration. The active ingredient, fillers, wetter and dispersant may also be milled together in one operation prior to addition of water.

For a WG formulation to be acceptable an additional requirement is that the said granules should readily disperse in water back to the primary dispersed particle size within a short period. This property is known as dispersibility and in describing the current invention it is measured as the time taken for granules to disperse back to primary particle size in water under a standard degree of agitation. A dispersion time of less than one minute is desirable, 20 seconds is excellent and 2 minutes is poor. Desirably the granules should also have good suspensibility. Suspensibility is typically tested using CIPAC MT 15.1. Above 80% is a desirable result, less than 60% is generally regarded as undesirable. In many cases when testing granules a so-called maximum surface coverage result is often obtained. This is where the suspensibility results reach a maximum level then plateau. Adding more dispersant will D not generally improve the result. This phenomenon is thought to be due to the particle size distribution of the material. Usually there is a given number of particles which are of such a size that they will settle regardless of type and concentration of dispersant.

Desirably the granules should have low wet sieve retention. Wet sieve retention is typically tested using CIPAC MT 59.3. For the 150 μm sieve less than 0.1% retained material is desirable. Less than 0.02% is more desirable. Likewise for the 53 μm sieve less than 0.6% is desirable, anything less than this is more desirable.

A further desirable property of a WG formulation is that the granules should be non-dusty and resistant to attrition. This is often a property of the method of granulation used and the level of compaction there obtained. Often there is an observed tradeoff between the dispersibility properties of a WG formulation and the level of compaction and attrition resistance. Attrition resistance may be measured by subjecting granules to a set degree of agitation and measuring the level of smaller particles generated by means of passing through sieves of various sizes.

Storage stability may be tested by storage at 50 degrees celsius and tested as above at 1 month and 3 month intervals to determine if any properties have changed significantly.

Preferably, the granules should maintain these properties on storage. Surprisingly, it has been observed that, upon prolonged storage, solid formulations such as WP and WG formulations containing dispersants such as those described herein are not as susceptible to deterioration in dispersability and suspensibility as formulations of the prior art.

We have also found that WP and WG formulations which incorporate the dispersants described herein require typically less dispersant, than for presently known WP and WG formulations.

As a further embodiment of the present invention in the case of WP and WG formulations the dispersants herein described may be combined with surfactant wetting agents selected from the classes comprising alkylpolysaccharides, dialkyl and monoalkylsulphosuccinate salts, nonionic surfactants loaded onto porous silicate carriers and urea surfactant complexes of non-ionic surfactants. The wetting agent may be combined in such formulations at a rate in excess of 1% w/w and preferably less than 3% w/w. Most preferred from the alkylpolysaccharide class of wetting agents are alkylpolyglucosides derived from reaction with glucose and a primary hydrocarbon alcohol. Even more preferred are the highly crystalline derivatives such as obtained from ECOTERIC AS 20 and ECOTERIC AS10 (Huntsman Corporation Australia Pty Ltd). Most preferred from the monoalkylsulphosuccinate class are sodium or potassium salts of cyclohexyl, iso-octyl and n-octyl sulphosuccinate. Most preferred from the dialkylsulphosuccinate class are sodium or potassium salts of dicyclobexyl, diisooctyl and di-n-octyl sulphosuccinates. Most preferred from the class of nonionic surfactants loaded onto insoluble porous silicate carriers are ethoxylated surfactants loaded onto carriers such as TERIC 157 (Huntsman Corporation Australia Pty Ltd). Most preferred wetting agents from the urea surfactant complexes are urea adducts of alcohol ethoxylate surfactants such as TERWET 7050 (Huntsman Corporation Australia Pty Ltd). The wetters herein described show good wettability and dispersibility for the formulations and have the additional advantage of showing storage stability in combination with the copolymer dispersants described. Whereas by comparison some commonly used WG and WP wetters such as alkylnaphthalene sulphonate salts and lignosulphonate salts have been found to show poor storage stability.

In the case of SC formulations in the present invention an active ingredient is typically added to water containing a dispersant, preferably with a surfactant wetting agent together with a conventional non-ionic dispersant. A humectant may also be included. A dispersion is formed using high shear mixing. The dispersion is then milled by any one of several means of wet milling so that the mean particle size of the dispersed solid is below 5 μm more typically in the range of from 1 to 3 μm. The resulting product is known as a millbase and may be modified with additives such as antifreeze, thickeners and antisettling agents, biocides and colouring agents may be added. For an SC formulation to be acceptable it should not show a high degree of thickening, settling or growth of aggregates over time. These physical properties can be assessed by visual observation.

SC's generally require good viscosity and storage stability. Storage stability is usually assessed as degree of top settling or syneresis, sedimenting or “claying” which is the tendency to form a sticky layer on the bottom and “bleeding” which is the tendency of the dispersion to separate without necessarily displaying even settling. Redispersibility is also important. These may also be assessed visually.

For SC formulations in the case of dispersants described herein only certain dispersant copolymers are suitable. When used alone, some dispersant copolymer derivatives give a viscosity of slurry premix unsuitable for milling so it is preferable to combine the dispersant with another fast acting well known dispersant such as an EO/PO block co-polymer type dispersant. While not wishing to be bound by theory it appears that the dispersant needs time to migrate to the surface of the dispersed particles. The dispersant copolymers are used synergistically with other known dispersants in some cases.

While the present invention has been described with reference to agrochemical formulations, it will be apparent that the improvements in dispersibility and suspensibility will render the present invention useful in other applications. The present invention will now be further described with reference to the following non-limiting examples and figures. All percentages recited herein are by weight of the total composition unless otherwise specified.

EXAMPLE 1

A Simazine 900 g/kg WG formulation of the following composition was prepared.

Simazine tech. (98% w/w) 91.8% w/w MORWET EFW  1.5 (Witco Corp) DISPERSANT  6.2 Water  0.5%

The dispersant used was an alkylnaphthalene formaldehyde condensate salt, SCS 2258 (ICI Surfactants). The granules were prepared by blending the solids with approximately 15% by weight of water such as to give a plastic premix which was then extruded using a Fuji-Paudal laboratory scale extrusion granulator. The resulting granules were then dried by means of a fluid bed drier back to a water content of approximately 0.5% w/w.

The resulting WG was tested for dispersibility by recording the time in seconds required for total disintegration under uniform agitation. The suspensibility was tested according to CIPAC MT 15.1 and the wet sieve retention was tested using 150 micron and 53 micron sieves according to CIPAC MT 59.3. Results are recorded in TABLE 1.

EXAMPLE 2

A simazine 900 g/Kg WG was prepared and tested as described in example 1 where the dispersant used was POLYFON H (Westvaco Corp), a lignosulphonate salt. The results are described in TABLE 1.

EXAMPLE 3

A Simazine 900 g/kg WG formulation of the following composition was prepared:

Simazine tech. (98% w/w) 91.8% w/w ATPLUS G73050  1.5 (now sold under the trade mark TERSPERSE 7050 by Huntsman Corporation Australia Pty Ltd) DISPERSANT  3.1 Kaolin  3.1 Water  0.5%

The dispersant used was the sodium salt of an alternating copolymer of n-octene and maleic anhydride of approximate molecular weight 20,000 to 30,000. The granules were prepared m and tested in the manner described in Example 1. The results are shown in TABLE 1.

EXAMPLE 4

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 3 with the dispersant being the sodium salt of a copolymer of n-decene and maleic anhydride. Results are shown in TABLE 1.

EXAMPLE 5

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 3 with the dispersant being the sodium salt of a copolymer of diisobutylene and maleic anhydride of approximate molecular weight 30,000 to 40,000. Results are shown in TABLE 1.

EXAMPLE 6

A WG formulation was prepared and tested as described in Example 3 with the dispersant ng the sodium salt of SMA 1000 (Atochem Inc.) which is a 1:1 molar ratio copolymer of styrene and maleic anhydride. Results are shown in TABLE 1.

EXAMPLE 7

A WG formulation was prepared and tested as described in Example 3 with the dispersant being the sodium salt of SMA 3000 (Atochem Inc.) which is a 3:1 molar ratio copolymer of styrene and maleic anhydride. Results are shown in TABLE 1.

EXAMPLE 8

A WG formulation was prepared and tested as described in Example 3 with the dispersant being the sodium salt of GANTREZ AN 119 resin (Rhodia Inc.) which is a copolymer of methylvinyl ether and maleic anhydride. Results are shown in TABLE 1.

EXAMPLE 9

A Simazine 900 g/kg WG formulation of the following composition was prepared.

Simazine tech. (98% w/w) 91.8% w/w ATPLUS G73050  1.5 (now sold under the trade mark TERSPERSE 7050 by Huntsman Corporation Australia Pty Ltd) DISPERSANT  6.2 Water  0.5%

The dispersant used was the monoammonium salt of an alternating copolymer of diisobutylene and maleic anhydride. The granules were prepared and tested in the manner described in Example 1. Results are shown in TABLE 1.

EXAMPLE 10

A Simazine 900 g/kg WG formulation of the following composition was prepared:

Simazine tech. (98% w/w) 91.8% w/w ATPLUS G73050  1.5 (now sold under the trade mark TERSPERSE 7050 by Huntsman Corporation Australia Pty Ltd) DISPERSANT  3.1 Kaolin  3.1 Water  0.5%

The dispersant used was the sodium salt of an alternating copolymer of undecylenic acid and maleic anhydride. The granules were prepared and tested in the manner described in example 1. Results are shown in TABLE 2.

EXAMPLE 11

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of an alternating copolymer of vinyl isobutyl ether and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 12

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of an alternating copolymer of alphamethyl styrene and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 13

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of a non-alternating copolymer of 10:3 molar ratio alphamethyl styrene:maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 14

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of a non-alternating copolymer of 4:3 molar ratio alphamethyl styrene: maleic anhydride. Results are shown in TABLE 2

EXAMPLE 15

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of a non-alternating copolymer of alphamethyl styrene and maleic anhydride made using a 50% molar excess of maleic anhydride. Results are shown in TABLE 2

EXAMPLE 16

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the benzyltrimethylammonium salt of an alternating co-polymer of alphamethyl styrene and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 17

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of an alternating copolymer of d-limonene and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 18

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of an alternating copolymer of P-pinene and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 19

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of an alternating copolymer of dimethyldicyclopentadiene and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 20

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 10 with the dispersant being the sodium salt of an alternating copolymer of dicyclopentadiene and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 21

An Atrazine 900 g/kg WG formulation of the following composition was prepared.

ATPLUS G73050 1.5 (now sold under the trade mark TERSPERSE 7050 by Huntsman Corporation Australia Pty Ltd) DISPERSANT 3.1 Kaolin 3.1 Water 0.5 where the dispersant used was the sodium salt of an alternating copolymer of dicyclopentadiene and maleic anhydride. The granules were made and tested as described in Example 1. Results are shown in TABLE 2.

EXAMPLE 22

An Atrazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 21 with the dispersant being the sodium salt of an alternating copolymer of alphamethylstyrene and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 23

A Diuron 900 g/kg WG formulation of the following composition was prepared.

Diuron tech. (97% w/w) 92.8% w/w ATPLUS G73050  1.5 (now sold under the trade mark TERSPERSE 3050 by Huntsman Corporation Australia Pty Ltd) DISPERSANT  3.1 Kaolin  2.1 Water  0.5 where the dispersant used was the sodium salt of an alternating copolymer of dicyclopentadiene and maleic anhydride. The granules were made and tested as described in example 1. Results are shown in TABLE 2.

EXAMPLE 24

A Diuron 900 g/kg WG formulation was prepared and tested in the manner described in a example 23 with the dispersant being the sodium salt of an alternating co-polymer of alphamethylstyrene and maleic anhydride. Results are shown in TABLE 2.

EXAMPLE 25

A Simazine 900 g/kg WG formulation of the following composition was prepared:

Simazine tech. (98% w/w) 91.8% w/w ATPLUS G73050  1.5 (now sold under the trade mark TERSPERSE 7050 by Huntsman Corporation Australia Pty Ltd) DISPERSANT  3.1 Kaolin  3.1 Water  0.5%

The dispersant used was the sodium salt of a terpolymer not of alternating character between comonomers of first and second type comprising alphamethylstyrene, styrene and maleic anhydride. The granules were prepared and tested in the manner described in example 1. Results are shown in TABLE 2.

EXAMPLE 26

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 25 with the dispersant being the sodium salt of a terpolymer of alternating character between monomers of first and second type comprising alphamethyl styrene, dicyclopentadiene and maleic anhydride. Results are shown in TABLE 2

EXAMPLE 27

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 25 with the dispersant being the sodium salt of a terpolymer of alternating character between monomers of first and second type comprising alphamethyl styrene: methacrylic acid: maleic anhydride in the molar ratio 40:20:40. Results are shown in TABLE 2

EXAMPLE 28

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 25 with the dispersant being the sodium salt of a terpolymer of alternating character between monomers of first and second type comprising alphamethyl styrene: methacrylic acid: maleic anhydride in the molar ratio 45:10:45. Results are shown in TABLE 2

EXAMPLE 29

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 25 with the dispersant being the sodium salt of a terpolymer of alternating character between monomers of first and second type comprising alphamethyl styrene: methacrylic acid: maleic anhydride in the molar ratio 48:2:48. Results are shown in TABLE 2

EXAMPLE 30

Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 25 with the dispersant being the sodium salt of a terpolymer of alternating character between monomers of first and second type comprising alphamethyl styrene: 4-vinylpyridine: maleic anhydride in the molar ratio 37.5:25:37.5. Results are shown in TABLE 2.

EXAMPLE 31

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 25 with the dispersant being the sodium salt of a terpolymer of alternating character between monomers of first and second type comprising alphamethyl styrene N-vinyl-2-pyrrolidinone: maleic anhydride in the molar ratio 37.5:25:37.5. Results are shown in TABLE 2

EXAMPLE 32

A Simazine 900 g/kg WG formulation was prepared and tested in the manner described in Example 25 with the dispersant being the sodium salt of a terpolymer of alternating character between monomers of first and second type comprising alphamethyl styrene 1-vinylimidazole: maleic anhydride in the molar ratio 48:4:48. Results are shown in TABLE 2

EXAMPLE 33

An Atrazine 900 g/kg WG formulation of the following composition was prepared.

ATPLUS G73050 1.5 (now sold under the trade mark TERSPERSE 3050 by Huntsman Corporation Australia Pty Ltd) DISPERSANT 3.1 Kaolin 3.1 Water 0.5 with the dispersant being the sodium salt of a terpolymer of alternating character between monomers of first and second type-comprising alphamethyl styrene, dicyclopentadiene and maleic anhydride. The granules were made and tested as described in Example 1. Results are shown in TABLE 2.

EXAMPLE 34

A Simazine 900 g/kg WP formulation of the following composition was prepared by blending the following

Simazine tech. (98% w/w) 91.8% w/w ATPLUS G 73050  1.7 (now sold under the trade mark TERSPERSE 3050 by Huntsman Corporation Australia Pty Ltd) DISPERSANT  3.1 Kaolin  3.4 where the dispersant used was the sodium salt an alternating copolymer of dicyclopentadine and maleic anhydride. Results are shown in TABLE 3. The wettability of the WP was also measured according to CIPAC test MT 53.5.1.

EXAMPLE 35

A Simazine 900 g/kg WP formulation of the following composition was prepared and tested in the manner described in example 34 where the dispersant used was the sodium salt an alternating copolymer of dicyclopentadiene and maleic anhydride used at 3.1% w/w, the wetting agent was the sodium salt dicyclohexylsulphosuccinate used at 1.7% w/w. Results are shown in TABLE 3.

EXAMPLE 36

A Simazine 900 g/Kg WP formulation was prepared and tested as described in example 34 excepting that the wetting agent used was ECOTERIC AS 20 (Huntsman Corporation Australia Pty Ltd), an alkylpolysaccharide used at 1.7% w/w on an active basis (the product is a 50% solution in water). The results are shown in TABLE 3.

EXAMPLE 37

A Simazine 900 g/Kg WP formulation was prepared and tested as described in example 34 excepting that the wetting agent used was TERIC 157 (Huntsman Corporation Australia Pty Ltd) a nonionic wetter loaded onto an insoluble porous carrier used at 1.7% w/w. The results are shown in TABLE 3.

EXAMPLE 38

A Simazine 900 g/kg WG formulation of the following composition was prepared

Simazine tech. (98% w/w) 91.8% w/w WETTER  1.5 DISPERSANT  6.2 Water  0.5%

The dispersant used was the sodium salt of an alternating copolymer of alphamethylstyrene and maleic anhydride of approximate molecular weight 20,000 to 30,000 and the wetter used was MORWET EFW (Witco Corp) a sulphonated naphthalene derivative salt. The granules were prepared and tested in the manner described in Example 1. The results are shown in TABLE 4.

EXAMPLE 39

A Simazine 900 g/Kg WG formulation was prepared and tested in the manner described in example 38. The dispersant used was the sodium salt of an alternating copolymer of alphamethylstyrene and maleic anhydride and the wetter used was the sodium salt of dicyclohexylsulphosuccinate. The results are shown in TABLE 4.

EXAMPLE 40

A Simazine 900 g/Kg WG formulation was prepared and tested in the manner described in example 38. The dispersant used was the sodium salt of an alternating copolymer of alphamethylstyrene and maleic anhydride and the wetter used was the sodium salt of monocyclohexylsulphosuccinate. The results are shown in TABLE 4.

EXAMPLE 41

An Atrazine 900 g/Kg SC formulation of the following composition was prepared.

Monoethylene glycol 4.0 ATLOX 4896A 3 (now sold under the trade mark TERSPERSE 4896, Huntsman Corporation Australia Pty Ltd) DISPERSANT 2 Silicone antifoam 0.2 Rhodopol 23 0.2 (Rhodia Inc) Proxel GXL 20 0.1 (Zeneca plc) Water 55.0

The dispersant used was the sodium salt of an alternating copolymer of alphamethylstyrene and maleic anhydride. The SC was prepared by dissolving the monoethylene glycol, ATLOX 4896A (now sold under the trade mark TERSPERSE 4896, Huntsman Corporation Australia Pty Ltd) and DISPERSANT in 85% of the water and adding the Atrazine tech. and antifoam with vigorous mixing to form a slurry or millbase premix. The premix is then milled using a Dynomill laboratory scale bead mill to give a suitable particle size distribution of >98% of particles below 5 microns. The milibase thus obtained was then blended with Proxel GXL (Zeneca plc) and Rodopol 23 (Rhodia Inc) in a premix and then made up to the desired volume with the remaining water and mixed to a homogeneous mixture. The SC thus obtained was of usable viscosity and was found to be storage stable after storage at 2 degrees C. and 50 degrees C. for one month, with minimal syneresis and thickening and no claying, sedimentation or aggregates being observed.

EXAMPLE 42

It was attempted to make an SC formulation according to the formula and method of example 41 with 4% w/w of the sodium salt of an alternating copolymer of alphamethylstyrene and maleic anhydride and only 1% w/w ATLOX 4896A (now sold under the trade mark TERSPERSE 4896, Huntsman Corporation Australia Pty Ltd) being used. The resulting millbase premix was of a viscosity which would not allow it to be milled.

TABLE 1 WDG Results from Prior Art Dispersibility Suspensibility Wet Sieve Retention (%) Example (Seconds) (%) 150 μm 50 μm No. T₀ T₁ T₃ T₀ T₁ T₃ T₀ T₁ T₃ T₀ T₁ T₃ 1 52 46 44 82 63 69 0.087 0.41 2.2  0.033 1.53 1.70 2 58 45 46 80 68 70 0.029 1.09 0.92  0.486 4.1  4.70 3 36 — — 39 — — — — — — — — 4 33 — — 59 — — 0.002 — — 0.042 — — 5 60 54 50 72 78 71 0.02  0.02 0.016 0.15  0.21 0.28 6 55 — — 31 — — 0.027 — — 0.095 7 >280 — — <10 — — — — — — — — 8 53 — — 48 — — 0.002 — — 0.085 — — 9 >200 — — <10 — — — — — — — — T₀ initial results T₁ after 1 month storage at 50° C. T₃ after 3 months storage at 50° C.

TABLE 2 WG Formulations of Embodiment of this Patent Dispersibility Suspensibility Example (seconds) (%) Wet Sieve Retention (%) No T₀ T₁ T₃ T₀ T₁ T₃ T₀ T₁ T₃ T₀ T₁ T₃ 10 65 54 — 79 48 — 0 0.01 — 0.044 0.053 — 11 67 68 62 84 83 84 0 0.01 0 0.052 0.073 0.079 12 78 70 72 83 86 85 0.02 0.01 0.01 0.08 0.09 0.096 13 40 — — 55 — — 3.01 — — 2.49 — — 14 >120 77 3 1.7 15 >180 40 14.04 8.5 16 68 >180    — 83 66 — 0.014 1.04 — 0.119 5.81 — 17 60 72 54 86 83 84 0 0.01 0.01 0.06 0.05 0.05  18 55 40 50 85 85 84 0.01 0.01 0 0.051 0.058 0.058 19 29 32 28 86 86 87 0.012 0.01 0.01 0.044 0.048 0.051 20 40 43 56 85 87 88 0.01 0 0.01 0.06 0.048 0.084 21 56 50 * 86 86 * 0.014 — * 0.38 * 22 30 45 * 88 86 * 0.09 0.031 * 0.6 0.67 * 23 37 40 * 78 76 * 0.01 0 * 0.055 0.01 * 24 40 45 * 62 68 * 0.01 0 * 0.581 0.55 * 25 70 * * 70 * * 1.03 * * 2.65 * * 26 53 * * 79 * * * * 0.09 * * 27 50 59 * 85 84 * 0.01 0.01 * 0.12 0.08 * 28 43 56 81 80 * 0.02 0.56 * 0.2 0.11 * 29 37 48 81 71 * 0.01 1.81 * 0.38 2.64 * 30 118 * * 62 * * 0.029 * * 1.8 * * 31 70 * * 83 * * 0.09 * * 0.12 * * 32 45 * * 83 * * 0.04 * * 0.07 * * 33 42 * * 88 * * 0.02 * * 0.27 * * T₀ initial results T₁ after 1 month storage at 50° C. T₃ after 3 months storage at 50° C. * Data not yet available — Testing discontinued

TABLE 3 WP Test Results Simazine 900 g/kg with various wetters Example Static Wetting Time Suspensibility No (Seconds) (%) 34 79 78 35 67 78 36 68 79 37 60 79

TABLE 4 WG Test Results Simazine 900 g/kg with various wetters Dispersibility Suspensibility Example (seconds) (%) Wet Sieve Retention (%) No. T₀ T₁ T₀ T₁ T₀ T₁ T₀ T₁ 38 50 41 84 68 0.015 0.081 0.033 4.1 39 68 56 88 87 0.065 0.025 0.15 0.089 40 70 * 78 * 0.014 * 0.09 *

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features. 

1. A method of dispersing an active, water-insoluble, solid agrochemical principal in an aqueous solution comprising the following steps: (i) providing a formulation comprising at least one active, water-insoluble, solid agrochemical principal and at least one dispersant comprising a water-soluble, agriculturally acceptable derivative of an alternating copolymer or an agriculturally acceptable salt thereof wherein said alternating copolymer comprises at least one residue of a first comonomer and at least one residue of a second comonomer, wherein said first comonomer comprises an α,β-unsaturated oxyacid, or an anhydride or other derivative thereof; and said second comonomer comprises an olefinic compound containing one or more polymerizable double bonds, or a derivative thereof; and (ii) dispersing said formulation in an aqueous medium to form a suspension of the active, water-insoluble, solid agrochemical principal; wherein said first comonomer is selected from the group consisting of fumaric acid and anhydride, and the esters, amides and imides derived from them; maleic acid esters, amides and imides; itaconic acid and anhydride and the corresponding esters, amides and imides derived from them; acrylic and methacrylic acids and the corresponding esters and amides derived from them; vinylphosphonic acid and the corresponding esters and amides derived from it; and ethylene sulphonic acid and the esters and amides derived from it.
 2. A method of dispersing an active, water-insoluble, solid agrochemical principal in an aqueous solution comprising the following steps: (i) providing a formulation comprising at least one active, water-insoluble, solid agrochemical principal and at least one dispersant comprising a water-soluble, agriculturally acceptable derivative of an alternating copolymer or an agriculturally acceptable salt thereof wherein said alternating copolymer comprises at least one residue of a first comonomer and at least one residue of a second comonomer, wherein said first comonomer comprises an α,β-unsaturated oxyacid, or an anhydride or other derivative thereof; and said second comonomer comprises an olefinic compound containing one or more polymerizable double bonds, or a derivative thereof; and (ii) dispersing said formulation in an aqueous medium to form a suspension of the active, water-insoluble, solid agrochemical principal, wherein said second comonomer is selected from the group consisting of styrene and its alkyl and halo derivatives, vinyl ethers and esters, internal olefins, exocyclic and endocyclic olefins, allylic alcohols and their corresponding ester derivatives, allylic ethers and allylic halo compounds, allylic aryl compounds, vinyl amides, vinyl chlorides and vinylidene chloride.
 3. A method according to claim 1 or 2 wherein the alternating copolymer has an alternating character defined by greater than 70% of consecutive comonomer residue units being alternate between residues of the first comonomer and the second comonomer.
 4. A method according to claim 1 or 2 wherein the alternating copolymer has an alternating character defined by greater than 90% of consecutive comonomer residue units being alternate between residues of the first comonomer and the second comonomer.
 5. A method according to claim 1 or 2 wherein the alternating copolymer contains additional comonomer residues which will not substantially change the alternating character of the copolymer.
 6. A method according to claim 2 wherein the first comonomer is selected from the group consisting of fumaric acid, maleic acid and anhydrides, and the esters, amides and imides derived from them; itaconic acids and anhydride and the corresponding esters amides and imides derived from them; acrylic and methacrylic acids and the corresponding esters and amides derived from them; vinylphosphonic acid and the corresponding esters and amides derived from it; and ethylene sulphonic acid and the esters and amides derived from it.
 7. A method according to claim 1 wherein the second comonomer is selected from the group consisting of styrene and its alkyl and halo derivatives, vinyl ethers and esters, α-olefins, internal olefins, exocyclic and endocyclic olefins, allyic alcohols and their corresponding ester derivatives, allylic ethers and allylic halo compounds, allylic aryl compounds, vinyl amides, vinyl chloride and vinylidene chloride. 